Cardioscope with variable sweep-timing means including superimposing recurring ekg complexes for display

ABSTRACT

This disclosure relates to a cardioscope including a cathode-ray tube and method for displaying superimposed succeeding groups of electrocardiac complexes. To superimpose the complexes occurrence of a first complex is detected and a timing cycle generated in response thereto and a sweep of the cathode-ray tube is initiated at the end of the timing cycle after occurrences of all the complexes of each group and before the occurrences of the first complex of the next group.

I United States Patent 1111 3,5 1,423

I 72] inventor Jerry H. Jacobson [56] References Cited 880 Fifth AWL.New York, N.Y. 10009 UNITED STATES PATENTS 1 P 524343 2,492,617 12/1949Boland 128/206 [22] Filed Feb. 2, 1966 1 Patented Fen 9,1971 2.9325494/1960 Klmg 346/110 3,215,136 11/1965 Holter 128/206 3,267,934 8/1966Thorton 128/206 3,457,452 7/1969 Saper 128/2.06X

Primary Examiner-William E. Kamm Attorney-Delio and Montgomery [54]CARDIOSCOPE WITH VARMBLE SWEEP'TIMING ABSTRACT: This disclosure relatesto a cardioscope includ- MEANS INCLUDING SUPERIMPOSING in a cathode-ratube and method for dis 1a in u rim- RECURRING EKG COMPLEXES FOR DISPLAYg P y g De 5 Cl 3 Dr posed succeedmg groups of electrocardiac complexes.To sualms awmg perimpose the complexes occurrence of a first complex isde- [52] US. Cl l28/2.06, tected and a timing cycle generated inresponse thereto and a 315/19 sweep of the cathode-ray tube is initiatedat the end of the tim- [51] Int. Cl i. A611) 5/04 ing cycle afteroccurrences of all the complexes of each group {50] Field of Search.128/1, 2, and before the occurrences of the first complex of the next2.06, 2.05, 201; 315/19; 324/121 group.

DEFLECTIDN DEFLECTlDN BETTE RY END LOW V LTRGEI V0 LTH 6E SUPPLYPATENTED FEB 9 Ian SHEET 1 OF 2 PATENTED res 9H7! 3.561.428

saw 2 or 2 INVENTOR Jen q H. Jacobson BY DJ, W9 WWW ATTOR NEYJCARDIOSCOPE WITH VARIABLE SWEEP-TIMING MEANS INCLUDING SUPERIMPOSINGRECURRING EKG COMPLEXES FOR DISPLAY This invention relates tocardioscopes, and more particularly relates to a small, portablecardioscope adapted to be carried by a physician on house calls,emergency calls and like missions.

At the present time there is no known device for monitoring theelectrocardiac activity of a patient or detecting suspected unusualheart activity without bringing the patient to the location of acardioscope, electrocardiograph, etc., such as a hospital, a clinic or,in some cases, a physician s office. Because of this, the presentinvention is intended to provide a small compact cardioscope which maybe easily carried in a physicians handbag or separate small carryingcase, and which the physician may have in his possession at allpotentially necessary times.

Because of the compactness of such a unit, the viewing screen of thecathode-ray tube of the device is necessarily small, and theelectrocardiac complexes which it can display are limited in number.This problem is amplified by the low frequency of electrocardiaccomplexes as compared to the frequency of electrical signals usuallydisplayed on an oscilloscope. Therefore, suitable compensation andoperating characteristics must be provided for the device to be useful.Due to the small size of the viewing screen, which may only be on theorder of l to l kinches, suitable means must be provided to present andretain low frequency signals on the small viewing screen.

Accordingly, the present invention provides new and improved means forpresenting electrocardiac intelligence on a small screen. This inventionprovides new and improved means for viewing cardiac activity throughcontrol of the sweep time of a cathode-ray tube and the manner in whichthe sweep is controlled by the occurrences of electrocardiac complexes.

Briefly stated, the invention, in one form thereof, provides in a newand improved manner, a plurality of cathode-ray tube sweep modes whichallow a physician to obtain an overall view of a plurality ofelectrocardiac complexes to indicate the regularity, amplitude andnormalcy of the complexes; a more detailed examination of a lesserplurality of complexes; and, if the patients pulse rate is fairlyregular, examination in detail of a single complex display which is theresult of superimposing reoccurring low frequency complexes to provide asingle complex display. The last-mentioned mode is accomplished by theprovision of novel sweep circuitry which is triggered by selectedcomplexes so that succeeding complex displays are superimposed on thedisplay screen to permit a detailed examination of a reoccurringcomplex, and the relationship of the modes thereof to each other.

An object of this invention is to provide a new and improved cardioscopeof small size and compactness which is adapted to be carried at alltimes by a physician.

Another object of this invention is to provide a new and improvedcardiosoope having a cathode-ray tube display screen of very small sizewhich will still permit a detailed examination of electrocardiacactivity.

Another object of this invention is to provide a cardioscope of smallsize having a new and improved cathode-ray tube sweep circuit whichpermits a detailed examination of electrocardiac activity.

A further object of this invention is to provide a cardioscope having anew and improved sweep circuit which allows the superimposing of aplurality of reoccurring electrocardiac complex displays on a very smallviewing screen to present to the observer a detailed examination of acomplex, and allows the physician to observe the electrocardiaccomplexes as they occur and also in groupings of two or more complexes.

A still further object of this invention is to provide new and improvedsmall cardioscope viewing screen, together with a grid system, formeasuring time duration and amplitude.

The features of the invention which are believed to be novel are pointedout with particularity and distinctly claimed in the concluding portionof this specification. The invention, however, both as to itsorganization and operation, together with further objects and advantagesthereof, may best be appreciated by reference to the following detaileddescription, taken in conjunction with the drawings, in which:

FIG. 1 is a diagram, partly schematic and partly in block form, showingthe electrical network of a cardioscope embodying the invention;

FIG. 2 is a graphical representation of a series of reoccurringelectrocardiac complexes; and

FIG. 3 is a view of the display of an electrocardiac complex on acathode-ray tube of relatively small size, together with a calibrationand timing means embodying the invention.

Referring now to the drawings, a cardioscope embodying the invention isgenerally represented by the reference numeral l0, and includes acathode-ray tube (CRT) 11, having a viewing screen 12 with longpersistency display coatings, vertical deflection means in the form ofplates 13, and horizontal deflection means in the form of plates I4. CRTII further includes the usual grid and cathode system (not shown).Cardioscope I0 includes an integral power system which comprises abattery and power pack IS, a voltage converter 16, and high andlow-voltage supplies I7 and I8, respectively. The high-voltage supply 17supplies the necessary high voltage for operation of the CRT and thelow-voltage supply I8 supplies the operating voltages +V and V forcardioscope I0. The power system also includes a battery charger I9adapted to recharge the battery which may have a service time of six toeight hours before requiring recharging. Charger 19 is adapted to beconnected to a source of household voltage, 1 l7 volts AC. The verticaldeflection of the cathode ray beam is controlled from a verticaldeflection amplifier 20 which receives an input from terminals 21connectable to electrodes (not shown) adapted to be operative arrangedon the subject's wrists. Another input terminal 21a receives a commonsignal from an electrode on a subjects ankle. Selector switch 22 isadapted to be switched between an operative position, as shown, to asource of a calibration signal. Vertical deflection amplifier 20includes a low level amplifier with a differential amplification ofabout 10,000. The amplified electrocardiac signals from temiinals 21directly drive the vertical deflection system of CRT 11 and thusmodulate the horizontal sweep thereof. Amplifier 20 includes verticalgain and vertical position adjusting potentiometers 20a and 20b,respectively.

The output of vertical amplifier 20 is also applied over lines 25 andthrough a polarity selector switch PS to an amplifier 26 in thehorizontal sweep circuit. It is to be understood that, as used herein,the terms horizonta.l" and vertical" are relative and refer to onecircuit being displaced with respect to the other.

The horizontal sweep circuit further comprises a timing or delaygenerating means 27, a sweep generator switching circuit 28, a sweepgenerator 29, a horizontal deflection amplifier 30, and a free-runningoscillator 31. Amplifier 30 may include horizontal gain and positionadjusting potentiometers 30a and 301;, respectively. The horizontalsweep may be synchronized to the input signal at terminals 21 by meansof the output of vertical deflection amplifier 20 over lines 25 toamplifier 26.

By way of example, and for purposes of disclosure only, the time delaygenerating means 27 is illustrated as comprising a one-shotmultivibrator 32 having means for varying the duration of its unstablecondition in the form of a potentiometer 33. One-shot multivibratorincludes two transistors TI and T2, together with conventionalcircuitry. The sweep generator switching circuit 28 is shown as abistable multivibrator or flipflop 35, including transistors T3 and T4in a conventional circuit arrangement, which may be set in one stablecondition through a differentiating or pulse-shaping circuit 36.Flip-flop 35 is reset over line 37 as hereinafter described. An outputsignal at the right side of flip-flop 35 is applied over a line 38 to atiming circuit 39 in sweep generator 29, which includes a transistor T5.The timing circuit 39 comprises a capacitor 40 selectively connectableto one of a plurality of timing resistances 41, 42 and 43 to control andpredetermine the horizontal sweep time or period. A transistor amplifierT6 in the form of an emitter follower is connected across capacitor 40and furnishes, through voltage divider 44, a sweep signal to horizontaldeflection amplifier 30. Transistor T6 also supplies a reset signalderived from the emitter thereof to flip-flop 35 over line 37.

Oscillator 31 is in the form of a free-running multivibrator 45 havingtransistors T7 and T8 in a typical Eccles-Jordan configuration. Thewaveform at the collector of transistor T8 may be selectively applied toflip-flop 35, as hereinafter described.

The embodiment of the invention, as disclosed, has three operationalmodes which will be described in specific examples. However, it is to beunderstood that the examples set forth are illustrative only. The threeoperational modes are hereinafter identified as I, II, and III, and arechosen through ganged mode selector switches MSK, M82, M83 and M54, eachhaving a contact arm adapted to selectively make contact with a terminalI, II or III corresponding to the operational mode selected.

Free-running oscillator 31 controls the sweep during operation in modeI, but during operation in modes II and III the base of transistor T7 isconnected to ground through selector switch M82 and, more specifically,terminals II or III thereof and the free-running multivibrator isdisabled.

During mode Il operation, free-running oscillator 31 is disabled asheretofore explained, and a synchronization signal received by amplifier26 from amplifier 20 is applied by switch MSl at terminal II thereofover line 47 to the collector of transistor T4, flip-flop 35, and henceby cross connection to the base of transistor T3. Such synchronizationsignal is effective to set flip-flop 35.

During mode III operation, the synchronization signal from amplifier 26is applied through mode selector switch MSl to terminal III thereof toinitiate a timing cycle of the delay or timing generator 27. After apredetermined time delay, when transistor T2 switches from its unstablecondition at the end of the time delay, a pulse L is applied topulse-shaping circuit 36 through terminal III of mode selector switchM83 to flip-flop 35 and the pulse M-shaped by circuit 36 sets flip-flop35.

When flip-flop 35 is switched to a set condition, the signal appearingat the collector of transistor T4 is effective to turn off transistor Tin sweep generator 29, and initiate a sweep cycle.

If mode I is selected, the input to the delay circuit 27 is grounded anddelay circuit 27 is disabled, the base of transistor T7 is removed fromground, oscillator 31 will operate in its normal free-running mode, theoutput of amplifier 26 is open ended, and thus there is nosynchronization of the sweep with the vertical deflection amplifier.Each time transistor T8 switches on and then off, a positive-goingrectangular pulse U is supplied through selector switch M83 and terminalI thereof to pulse shaping circuit 36. The shaped pulse M is thenapplied through diode D2 to the base of transistor T3 and flip-flop 35.Transistor T3 is normally conducting and transistor T4 normallynonconducting when flip-flop 35 is in a reset state. The positive-goingpulse to the base of transistor T3 is a setting signal which turnstransistor T3 off and produces a negative-going voltage N at thecollector thereof.

This turns transistor T4 on by the usual cross connection action and thecollector thereof rises essentially to ground potential to generate avoltage 0. Therefore, the emitter base circuit of transistor T5 in sweepgenerator 29 is back-biased and transistor T5 is turned off. Capacitor40 now commences to charge and the voltage at the collector oftransistor T5 decreases in a linear manner. The base of transistor T6 isconnected to the collector of transistor T5 and as the potential at thecollector of transistor T5 linearly decreases, the potential at theemitter of transistor T6 linearly decreases to provide a ramp functionand generate the sweep voltage W which is applied to horizontaldeflection amplifier 3d, from voltage divider 44. When the voltage atthe emitter of transistor T6 decreases to a predetermined value towardsV, diode D1 will conduct current from +V through resistance 53 over line37 and the negative-going voltage at the base of transistor T3 will turntransistor T3 on, and reset flip-flop 35. Resistance 53 is substantiallygreater than resistances 54, 52 and 55. By cross connection transistorT4 is turned off, and by voltage divider action of resistances 50, 51and 52, the collector of transistor T4 and the base of transistor T5, gonegative. Resistance 50 is substantially greater than resistances 51 and52. This turns on transistor T5 and interrupts the charging of capacitor40 and a sweep cycle is completed. Thereafter, another sweep cycle maybe generated when transistor T5 is again turned off. The timingwaveforms are shownat V and the output waveform of transistor T6 isshown at W. In mode I, the sweep is freerunning, controlled byoscillator 31 with no external synchronization. Therefore, a number ofelectrocardiac complexes, as shown in FIG. 2, will appear on the screen12, predetermined by the time of the sweep. If, for example, the sweeptime is 3 seconds, and the subject has a pulse rate of I00 pulses perminute, five complexes may be displayed during each sweep.

From this, the physician may determine the pulse rate, the regularity ofthe pulses and the amplitude thereof. If the complexes are highlyirregular, or very small in amplitude, the physician may not deem itnecessary to operate the scope in modes II and III. He has, at thistime, found out quite a bit of intelligence in terms of overall generalassessment of the subjects clinical condition and will probably wish tohave further more exhaustive tests of the patients cardiac condition ina more controlled environment with more complex instruments, and willprobably wish to run a complete electrocardiograph or vectorcardiographon the patient.

Assume that the electrocardiac complexes are reasonably regular, thenthe physician may make a somewhat more detailed examination of thecomplexes by switching to mode ll of operation. This is accomplished bymoving ganged selector switches MS to terminal II. In this mode thehorizontal sweep circuit is synchronized with the occurrence of thecomplexes through the output of the vertical deflection amplifier 20.The output of amplifier 26 is applied to tenninal II of selector switchMSl which is connected to the base of transistor T3 at the collector oftransistor T4, over line 47. In this mode of operation, flip-flop 35 isset by the occurrence of an electrocardiac complex, as shown in FIG. 2,applied to the base of transistor T3 over line 47. In this mode ofoperation, capacitor 40 charges through resistance 42, as selected inthis mode by selector switch M84 to provide a sweep of lesser durationthan in mode I, for example, 1.5 seconds. If the sweep time in mode IIis selected to be 1.5 seconds, at least one complex will occur duringeach sweep for a pulse rate as low as 40 beats per minute and twocomplexes will be seen for pulse rates greater than beats per minute. Atthe end of the fixed sweep time, flip-flop 35 is reset, as heretoforeexplained, and another sweep will not begin until occurrence of the nextcomplex following the end of the sweep.

Continuing with the assumption that the pulse rate is fairly regular,the physician will now switch to mode III. In this mode, the sweep timemay be fixed at a still smaller time, for example, 600 milliseconds, orless.

This sweep is also triggered by an electrocardiac complex. However, aseach complex occurs, a delay or timing period is initiated. When thedelay times itself out, the sweep starts. The technique involved here isto make the sweep occur during the occurrence of the next complex intime relation to occurrence of the previous complex. In this manner,each complex initiates the sweep for the succeeding complex. Thisprocess is repetitive and permits the superimposing of each succeedingcomplex as a single complex on the display, which may be the subject ofdetailed analysis. Also, by varying the delay, as hereinafter explained,one can make the complex appear to slide to the left or right of thedisplay. In mode III operation, all selector switches MS are at terminalI, the sweep generasllll tor is synchronized with the input at thevertical deflection amplifier. Reference is made to FIG. 2 which shows asubstantially uniform train of electrocardiac complexes, A, B, C, D, E,commencing at time t At time I when the QR portion of complex A hasrisen to a value y, it actuates the delay means here exemplified asone-shot multivibrator 32 which is set to an unstable condition. Thenthe delay times out at time transistor T2 turns on and a positive-goingvoltage L is applied to pulse-shaping circuit 36 to set flip-flop 35.Thereafter, the operation of flip-flop 35 and sweep circuit 29 is asheretofore described with the exception that capacitor 40 chargesthrough resistance 43 to provide a predetermined sweep time, shown inFIG. 2, as t,t to display complex B. During the interval to 1,, andwhile complex B is being displayed, as shownin H6. 3,, portion OR ofcomplex B at amplitude y and time triggers delay circuit 37 to initiateanother sweep at time 2 This display of each complex and the use of eachcomplex to set a delay, and then at the end of such delay, trigger thesweep circuit before occurrence of the next complex reoccurscontinuously while the scope is in mode lll operation. This results inthe superimposing of a single complex, as shown on the face 12 of thescope in FIG. 3. This technique permits a continuous display of a verylow frequency recurring signal.

To follow through with the description of FIG. 2, at time 1,, the delaytimes out and the sweep circuit is triggered to display complex C. Attime complex C, initiates another delay which times out at time 2 Thencomplex D is superimposed on complex C during the next sweep from t,,t,

It will be noted that the delay times 1 -1,; r,r 2 -1 and t,,-t-, are oflesser time than the sweep time, exemplified as I -r,; :,,-r,,; z,,-1,,;and r,,-r,,,.

if in mode llll operation, the sweep time is chosen to be, say, 600milliseconds, the face plate 60 surrounding the face 12 of the CRT maybe calibrated into a predetermined number or graduations, each of whichwould indicate a time interval. lf, for example, there were six verticalgraduations 61, each would indicate an interval of 100 milliseconds.Thus the spaces between the graduations would be an integral factor ofthe sweep time of the CRT. With this information, the physi' cian maydetermine the time between the various nodes or other parts of thecomplex; for example, the time between the T and 0 nodes, the timebetween the Q and S nodes, etc. Moreover, by varying the delay as byadjusting potentiometer 33 in one-shot multivibrator 32, the physicianmay move any portion of the complex displayed on the face 12 to coincidewith a calibration which may be used as a base to time its relation withother portions of the complex. In this manner, any point of the complexmay be used as a base to time the other portions relative thereto.Similarly, the horizontal position may be varied so that the amplitudesof the nodes may be compared with the horizontal graduations 62.

To calibrate the amplitude of the input waveform, and also as a check onthe battery voltage, the essentially rectangular output waveform offree-running multivibrator 45 is applied over lines 56 to terminals 23of calibration switch 22. The calibration signal is taken from similarvoltage dividers 57 and 58 connected across the collector and emitter ofeach of transistors T7 and T8, respectively. Prior to using the scope,the physician, without an input signal on terminals 21, may movecalibration switch 22 to terminals 23 and observe the waveform of theoutput of multivibrator 35. Then, by the vertical positioningadjustment, this waveform may be displayed. in a desired position on theface 12 of the CRT 11 in predetermined relationship with horizontalgraduations 62. Additionally, the failure of such signal to reach apredetennined amplitude upon adjustment of the gain control willindicate that the batteries require recharging.

it will be understood that the timing of the delay and the sweep may besuch as to present every succeeding pair of complexes superimposed.Assume, for example, that the sweep time is 1.2 milliseconds, and thedelay was set to be effective from time t, to time then a sweep would beinitiated at time t, and would last until time 1,, and display complexesC and D. During this display period, from time t, to 1,, and,specifically, at time i complex C would trigger the delay circuit andtime out at time I, to commence a sweep which would display complex Eand the succeeding complex. During this sweep and at time complex Ewould again trigger the delay. In this manner, the delay and the sweeptime may be so arranged as to superposition each succeeding pair ofcomplexes on the preceding pair of complexes. In a similar manner, thesweep time may be decreased to display only a portion of a complex formore detailed study. It will be understood that the various sweep timesare set forth only for purposes of illustration. Moreover, the modes ofoperation may be so chosen that both modes I and ll display superimposedsucceeding complexes or portions thereof.

The expected range of times of an electrocardiac complex as measuredbetween nodes (FIG. 3) is P to Q .O70. l20 milliseconds P to R .l20.20Omilliseconds Q to S .050-. milliseconds Q to T .260-.450 milliseconds [fthe physician wishes to view and investigate only a portion of acomplex, a sweep time of, say, 300 milliseconds might be selected. Asrelated to this, the duration of a complex might be close to 600milliseconds. For example, the delay commencing at amplitude y of anycomplex may be set in relation to the sweep time, or vice versa, to timeout subsequent to the succeeding P and 0 nodes on the QR wave to displayonly the R, S, and T nodes of the complex. Alternatively, the delay maybe set in relation to the sweep time, or vice versa, such that only thePOR nodes were displayed.

it may thus be seen that the objects of the invention set forth above aswell as those made apparent from the preceding description areefficiently attained, and while a preferred embodiment of the inventionhas been set forth for purposes of disclosure, other embodiments to theinvention as well as modifications to the disclosed embodiments theretomay occur to those skilled in the art. Accordingly, the appended claimsare intended to cover all embodiments of the invention and modificationsthereof which do not depart from the spirit and scope of the invention.

1 claim:

1. In a cardioscope including a cathode-ray tube having a viewing screenfor displaying an electrocardiac complex, means for controlling andtiming the sweep of the cathode-ray tube and means for modulating thesweep of the cathode-ray tube with electrocardiac complexes; timingmeans responsive to occurrences of a complex for initiating a timingcycle, means responsive to the end of said timing cycles to initiate asweep a predetermined time after occurrence of each complex and prior tooccurrence of the next complex so as to superimpose such complex displayon the preceding complex displays, a platelike member having edgesdefining an aperture adapted to surround the viewing screen, said memberhaving calibration marks, said marks being of such number that eachspace defined therebetween is an integral factor of the sweep time ofthe cathode-ray tube.

2. A cardioscope including a cathode-ray tube having a viewing screenfor displaying an electrocardiac complex or portion thereof, means forcontrolling and timing the sweep of the tube to display anelectrocardiac complex or portion thereof, a platelike member havingedges defining an aperture adapted to surround the viewing screen, saidmember having calibration marks, said marks being of such number thateach space defined therebetween is an integral factor of the sweep timeof the cathode-ray tube.

3. A cardioscope including a cathode-ray tube having a viewing screenadapted to display electrocardiac complexes, said cathode-ray tubehaving horizontal and vertical deflection means, a sweep circuitoperatively connected to one of said deflection means, means forapplying electrocardiac signals to the other of said deflection means,circuit means for synchronizing said sweep generator to occurrence ofelectrocardiac complexes, time delay means, said time delay means beingresponsive to occurrence of a complex for actuating said sweep generatora predetermined time before or during occurrences of the next complex,and selection means for actuating said sweep generator either throughsaid delay means or directly upon occurrence of complexes, saidselection means being operative to predetermine the timing of the sweepgenerator in response to the mode of operation selected.

4. The cardioscope of claim 3 further including means for varying thedelay of said time delay means.

5. A cardioscope including a cathode-ray tube having a viewing screen,vertical and horizontal deflection means, means for controlling one ofsaid deflection means to produce a sweep of the cathode-ray beam acrossthe viewing screen, and means for applyin'g'elctrocardiac complexes to'the other of said deflection means to modulate the sweep of saidcathode-ray beam and display the complex, comprising a sweep generatorconnected to said first of the deflection means, said sweep generatorhaving selection means effective to predetermine the time to sweep ofthe cathode-ray beam across said viewing screen, resettable switchingmeans effective to trigger said sweep generator and produce a sweep,said switching means being responsive to completion of the sweep to bereset, first and second means for actuating said switching means andselection means for choosing said first or second means, said firstmeans comprising a free-running oscillator effective to repetitively setsaid switching means and produce sweeps at a first time rate, saidsecond means being effective upon selection thereof to set saidswitching means upon occurrence of a complex, delay means. and means foractuating said delay means in response to occurrence of a complex, saiddelay means being connectable to said switching means to set saidswitching means at the expiration of the delay provided by said delaymeans.

1. In a cardioscope including a cathode-ray tube having a viewing screenfor displaying an electrocardiac complex, means for controlling andtiming the sweep of the cathode-ray tube and means for modulating thesweep of the cathode-ray tube with electrocardiac complexes; timingmeans responsive to occurrences of a complex for initiating a timingcycle, means responsive to the end of said timing cycles to initiate asweep a predetermined time after occurrence of each complex and prior tooccurrence of the next complex so as to superimpose such complex displayon the preceding complex displays, a platelike member having edgesdefining an aperture adapted to surround the viewing screen, said memberhaving calibration marks, said marks being of such number that eachspace defined therebetween is an integral factor of the sweep time ofthe cathode-ray tube.
 2. A cardioscope including a cathode-ray tubehaving a viewing screen for displaying an electrocardiac complex orportion thereof, means for controlling and timing the sweep of the tubeto display an electrocardiac complex or portion thereof, a platelikemember having edges defining an aperture adapted to surround the viewingscreen, said member having calibration marks, said marks being of suchnumber that each space defined therebetween is an integral factor of thesweep time of the cathode-ray tube.
 3. A cardioscope including acathode-ray tube having a viewing screen adapted to displayelectrocardiac complexes, said cathode-ray tube having horizontal andvertical deflection means, a sweep circuit operatively connected to oneof said deflection means, means for applying electrocardiac signals tothe other of said deflection means, circuit means for synchronizing saidsweep generator to occurrence of electrocardiac complexes, time delaymeans, said time delay means being responsive to occurrence of a complexfor actuating said sweep generator a predetermined time before or duringoccurrences of the next complex, and selection means for actuating saidsweep generator either through said delay means or directly uponoccurrence of complexes, said selection means being operative topredetermine the timing of the sweep generator in response to the modeof operation selected.
 4. The cardioscope of claim 3 further includingmeans for varying the delay of said time delay means.
 5. A cardioscopeincluding a cathode-ray tube having a viewing screen, vertical andhorizontal deflection means, means for controlling oNe of saiddeflection means to produce a sweep of the cathode-ray beam across theviewing screen, and means for applying electrocardiac complexes to theother of said deflection means to modulate the sweep of said cathode-raybeam and display the complex, comprising a sweep generator connected tosaid first of the deflection means, said sweep generator havingselection means effective to predetermine the time to sweep of thecathode-ray beam across said viewing screen, resettable switching meanseffective to trigger said sweep generator and produce a sweep, saidswitching means being responsive to completion of the sweep to be reset,first and second means for actuating said switching means and selectionmeans for choosing said first or second means, said first meanscomprising a free-running oscillator effective to repetitively set saidswitching means and produce sweeps at a first time rate, said secondmeans being effective upon selection thereof to set said switching meansupon occurrence of a complex, delay means, and means for actuating saiddelay means in response to occurrence of a complex, said delay meansbeing connectable to said switching means to set said switching means atthe expiration of the delay provided by said delay means.